Compatible optical pick-up apparatus for recording and reproducing information from recording media having different formats

ABSTRACT

An optical pick-up apparatus for recording and reproducing information from recording media using a first, second, and third light source to emit light beams having various wavelengths corresponding to a first, second and third recording media, respectively. A dichroic beam splitter has a first, second, and third input surface for receiving the light beams emitted from the first, second and third light sources, respectively, and an output surface through which the light beams received through the input surfaces is transmitted toward the first, second, and third recording media. A converging device converges the light beams transmitted through the output surface of the dichroic beam splitter toward the first, second, and third recording media, and a photodetector receives light beams reflected from the first, second, and third recording media that has been transmitted through the dichroic beam splitter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No. 98-8644,filed Mar. 14, 1998 in the Korean Patent Office, the disclosure of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a compatible optical pick-up apparatusfor recording and reproducing information from recording media havingvarious formats, and more particularly, the present invention relates toan optical pickup apparatus for recording and reproducing informationfrom recording media using light sources to emit light beams havingdifferent wavelengths corresponding to the recording media of thevarious formats.

2. Description of the Related Art

An optical pick-up apparatus employed in a compact disk player (CDP), adigital versatile disk player (DVDP), a CD-ROM driver or a DVD-ROMdriver, records and/or reproduces information on or from a recordingmedium in a non-contact manner. The recording medium has a standardizedsize, so that an increase in the information recording density withrespect to a recording layer of a predetermined size is required, forwhich much research is currently being conducted.

A digital versatile disk (DVD) or a high density DVD (HD-DVD) is a highcapacity disk that is capable of recording a large amount ofinformation. The DVD has a standardized thickness that differs from thethickness of CD related devices, such as a compact disk (CD), aCD-recordable (CD-R) medium, a CD-I, and a CD-G, with reference to anallowable error of a mechanical disk gradient and a numerical apertureof an object lens.

For example, the numerical aperture of the object lens of the opticalpick-up apparatus for recording and/or reproducing information on andfrom the CD is 0.45, while the numerical aperture of the optical pick-upapparatus for recording and/or reproducing information on and from theDVD is 0.6, in order to increase the recording and reproduction density.Due to an allowable error of the mechanical disk gradient that resultsfrom using an object lens having large numerical apertures, thethickness of the CD is 1.2 mm, and the thickness of the DVD is 0.6 mm.In the same way, the thickness of the HD-DVD also will be standardizedto 0.6 mm.

Furthermore, wavelengths of the reproducing light sources used for theDVD are different from those used for the CD. For example, thewavelength of a light source for reproducing information from aconventional CD is approximately 780 nm, while the wavelength of a lightsource for reproducing information from a conventional DVD is in a rangefrom approximately 635 nm to 650 nm. A light source emitting light beamsof a shorter wavelength in a range from approximately 410 nm to 420 nmis used when reproducing information from the HD-DVD.

The thicknesses of the CD and DVD differ so that if information isrecorded and/or reproduced on and from the CD by an optical pick-upapparatus for a DVD, a spherical aberration is generated due to thedifference in the thicknesses. Therefore, the optical intensity requiredto record the information cannot be obtained, or the reproducing signaldeteriorates.

A compatible optical pick-up apparatus for a DVD that is capable ofreproducing information from a CD includes a light source that emits alight beam that has a wavelength of approximately 650 nm, a beamsplitter for directing incident light beams, an object lens forconverging a light beam to form a light spot on a recording surface of adisk, and a photodetector for detecting an error signal and aninformation signal. In this case, the numerical aperture of the objectlens is 0.6.

If an object lens, in which an annular optical control pattern isformed, is employed, the spherical aberration caused by the differencein the thicknesses of the disks can be compensated for, to therebycompatibly employ disks having different thicknesses.

In other words, the optical pick-up apparatus includes a light sourcefor the DVD and means capable of compensating for the difference inthicknesses of employed disks, to thereby allow CD reproduction. Whenreproducing information from the CD, deterioration of approximately 5%is generated, compared to an optical pick-up apparatus employing a lightsource for a CD emitting light beams that have a wavelength of 780 nm,which is within a range of a reproducing allowable error.

However, if a CD related device, such as a CD-R is employed, along withlight sources that have wavelengths of 650 nm and 780 nm, sensitivitiesare different from each other. For example, the CD-R includes arecording layer of an organic pigment film, so that a difference inreflectivities in accordance with wavelengths of light is great. As aresult, the reflectivity is high when using light beams that have awavelength of 780 nm, while the reflectivity deteriorates to 10% or lesswhen using light beams that have a wavelength of approximately 650 nm,to thereby reproduce no information.

In addition, in the optical pick-up apparatus for the HD-DVD thatemploys a light source emitting light beams that have a wavelength ofapproximately 410 nm, recording and reproduction with respect to a CD-Rand an expected DVD-R is not possible.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a compatible opticalpick-up apparatus allowing recording media having various formats tohave information recorded thereon and reproduced therefrom.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and, in part, will be obvious fromthe description, or may be learned by practice of the invention.

Accordingly, to achieve the above and other objects of the presentinvention, there is provided an optical pick-up apparatus for recordingand reproducing information from first, second, and third recordingmedia. A first light source emits a light beam that has a wavelengthcorresponding to the first recording medium, a second light source emitsa light beam that has a wavelength corresponding to the second recordingmedium, and a third light source emits a light beam that has awavelength corresponding to the third recording medium. A dichroic beamsplitter has a first input surface, a second input surface, and a thirdinput surface to receive the light beams emitted from the first, thesecond and the third light sources, respectively, and an output surfacethrough which the light beams received by the first, the second, and thethird input surfaces are transmitted toward the first, the second, andthe third recording media, respectively. A converging device convergesthe light beams transmitted through the output surface of the dichroicbeam splitter toward the first, the second, and the third recordingmedia, respectively, and photodetectors receive the light beamsreflected from the first, the second, and the third recording media,respectively.

The dichroic beam splitter has a first slant reflection surface totransmit the light beam output from the first light source and toreflect the light beam output from the second light source toward theoutput surface, and a second slant reflection surface to transmit thelight beam output from the first light source and to reflect the lightbeam emitted from the third light source toward the output surface. Thefirst and the second slant reflection surfaces are formed by alternatelyrepeatedly stacking dielectric layers having different refractivities,and the dielectric layers are preferably alternately formed of MgF₂ andTiO₂, SiO₂ and ZrO₂, Al₂O₃ and ZrO₂, MgF₂ and ZrO₂, SiO₂ and TiO₂, orAl₂O₃ and TiO₂,

Objects of the invention are also achieved by providing an opticalpick-up apparatus for recording and reproducing information from firstand second recording media that includes a first light source and asecond light source to emit light beams that have wavelengthscorresponding to the first and second recording media. A dichroic beamsplitter has input surfaces to receive the light beams emitted from thefirst and the second light sources, and an output surface through whichthe light beams received by the input surfaces are transmitted towardthe first and the second recording media, respectively. A convergingdevice converges the light beams transmitted through the output surfaceof the dichroic beam splitter to the first and the second recordingmedia, respectively, and photodetectors receive the light beamsreflected from the first and the second recording media, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objective and advantages of the present invention will becomemore apparent by describing in detail a preferred embodiment thereofwith reference to the attached drawings in which:

FIG. 1 is a schematic view of an optical arrangement of a compatibleoptical pick-up apparatus according to a first embodiment of the presentinvention;

FIGS. 2A and 2B are sectional views of a first slant reflection surfaceand a second slant reflection surface shown in FIG. 1, respectively;

FIG. 3 is a schematic view of another type of converging device for theoptical pickup apparatus of FIG. 1;

FIG. 4 is a schematic view of an optical arrangement of a compatibleoptical pick-up apparatus according to a second embodiment of thepresent invention; and

FIG. 5 is a schematic view of an optical arrangement of a compatibleoptical pick-up apparatus according to a third embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now made in detail to the present preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings, wherein like reference numerals refer to the likeelements throughout. The embodiments are described below in order toexplain the present invention by referring to the figures.

As illustrated in FIG. 1, a compatible optical pick-up apparatusaccording to a first embodiment of the present invention includes afirst light source 25, a second light source 35, and a third lightsource 45 that radiate corresponding light beams having differentwavelengths. A dichroic beam splitter 50 includes three input surfaces50 a, 50 b and 50 c receiving light beams from the first, second andthird light sources 25, 35 and 45, respectively, and an output surface50 d. A converging device 60 is arranged along a light path between thedichroic beam splitter 50 and a recording medium 10, and first throughthird photodetectors 27, 37 and 47 receive the light beams that arereflected from the recording medium 10 (of a corresponding type) andthat pass through the dichroic beam splitter 50.

The first light source 25 emits a light beam having a wavelength ofapproximately 5 410 nm, for reproducing information from an HD-DVD. Thesecond light source 35 and the third light source 45 emit light beamsthat have a wavelength of 650 nm and 780 nm for reproducing informationfrom a DVD and a CD, respectively. The light sources 25, 35 and 45 areselectively driven in accordance with the recording medium 10 that isemployed (loaded in an optical drive apparatus of an optical diskplayer).

The light beams reflected from the recording medium 10 (thecorresponding type loaded in the optical drive apparatus) are receivedin the first through third photodetectors 27, 37 and 47 through firstthrough third hologram elements 29, 39 and 49, respectively. The firstthrough third hologram elements 29, 39, and 49 function as light pathconverting means and are installed in light paths between the dichroicbeam splitter 50 and the first through third photodetectors 27, 37 and47, respectively.

The first through third light sources 25, 35 and 45 may be combined withthe first through third photodetectors 27, 37 and 47, respectively, toform first through third light modules 20, 30 and 40, respectively.

The first through third light sources 25, 35 and 45 and the firstthrough third photodetectors 27, 37 and 47 are installed oncorresponding bases 21 of the first through third light modules 20, 30and 40. Substrates 22 are respectively provided on the bases 21 and areelectrically connected to the corresponding first through third lightsources 25, 35 and 45 and the corresponding first through thirdphotodetectors 27, 37 and 47 with wires 24, and the first through thirdlight modules 20, 30 and 40 are connected to external circuits byrespective lead frames 23.

First through third hologram patterns 29 a, 39 a and 49 a are formed inthe hologram elements 29, 39 and 49, respectively, so that light beamsradiated from the first through third light sources 25, 35 and 45 aretransmitted to the corresponding types of the recording medium 10, andthe light beams reflected from the corresponding types of the recordingmedium 10 are diffracted and transmitted to the first through thirdphotodetectors 27, 37 and 47, respectively. The first through thirdhologram patterns 29 a, 39 a and 49 a may be changed in accordance withthe wavelengths of the light beams emitted from the light sources 25, 35and 45.

The first through third hologram elements 29, 39 and 49 are preferablycompactly modulated together with the respective first through thirdlight sources 25, 35 and 45 and the respective first through thirdphotodetectors 27, 37 and 47.

A beam splitter (not shown) may also be employed as the light pathconverting means, in which case the first through third photodetectors27, 37 and 47 would be arranged corresponding to the beam splitter.

The dichroic beam splitter 50 may be constructed by bringing four prismseach having a refractivity of, for example, 1.52, into contact with eachother. The paths of the light beams received from the first, second andthird light sources 25, 35 and 45 through the three input surfaces 50 a,50 b and 50 c of the dichroic beam splitter 50, respectively, arediverted to the output surface 50 d by a first slant reflection surface51 and a second slant reflection surface 53.

The first slant reflection surface 51 preferably transmits the lightbeams emitted from the first and third light sources 25 and 45 andreflects the light beam emitted from the second light source 35, and thesecond slant reflection surface 53 transmits the light beams emittedfrom the first and the second light sources 25 and 35 and reflects thelight beam emitted from the third light source 45. The first and secondslant reflection surfaces 51 and 53 are formed by repeatedly alternatelystacking dielectric layers having different refractivities in relationto an adjacent dielectric layer such that a light beam is selectivelytransmitted or reflected according to the wavelength of the light beam.

Preferably, MgF₂ having a refractivity of 1.38, SiO₂ having arefractivity of 1.46, Al₂O₃ having a refractivity of 1.64, ZrO₂ having arefractivity of 2.1 or TiO₂ having a refractivity of 2.3 may be used asthe dielectric materials.

As illustrated in FIG. 2A, the first slant reflection surface 51 isformed by repeatedly alternately stacking a first dielectric layer 51 aformed of MgF₂ which has a refractivity of approximately 1.38 and athickness of 0.3λ₁, and a second dielectric layer 51 b formed of TiO₂which has a refractivity of approximately 2.3 and a thickness of 0.5λ₁,where 80 ₁ indicates a reference wavelength of approximately 1040 nm.

If the first and second dielectric layers 51 a and 51 b are alternatelystacked with twenty layers, the reflectivities of the first slantreflection surface 51 with respect to light beams having wavelengths of410 nm, 650 nm and 780 nm become approximately 0.2%, 99.1% and 0.8%,respectively. As a result, the first slant reflection surface 51reflects most of the light beam that has a wavelength of approximately650 nm that is emitted from the second light source 35, and transmitsmost of the light beams emitted from the first and the third lightsources. 25 and 45.

As illustrated in FIG. 2B, the second slant reflection surface 53 isformed by repeatedly alternately stacking a third dielectric layer 53 aformed of MgF₂ which has a refractivity of approximately 1.38 and athickness of 0.3λ₂, and a fourth dielectric layer 53 b formed of TiO₂which has a refractivity of approximately 2.3 and a thickness of 0.5λ₂,where λ₂ indicates a reference wavelength of approximately 600 nm.

If the third and fourth dielectric layers 53 a and 53 b are alternatelystacked with twenty layers, the reflectivities of the second slantreflection surface 53 with respect to lights having wavelengths of 410nm, 650 nm and 780 nm become approximately 0.1%, 0.9% and 96.0%,respectively. As a result, the second slant reflection surface 53reflects most of the light beam having a wavelength of approximately 780nm that are emitted from the third light source 45, and transmits mostof the light beams that are emitted from the first and the second lightsources 25 and 35.

The reflectivities of the first and the second slant reflection surfaces51 and 53 can be controlled by changing the number of layers of thefirst through fourth dielectric layers 51 a, 51 b and 53 a, 53 b.

Alternatively, the first and the second slant reflection surfaces 51 and53 may be formed by repeatedly stacking dielectric layers of SiO₂ andZrO₂, Al₂O₃ and ZrO₂, MgF₂ and ZrO₂, SiO₂ and TiO₂ or Al₂O₃ and TiO₂,rather than MgF₂ and TiO₂.

If the position of the first light source 25 is changed with that of thesecond light source 35 or the third light source 45, the first or thesecond slant reflection surface 51 or 53 is preferably formed byrepeatedly stacking a first dielectric layer (not shown) formed of MgF₂having a refractivity of approximately 1.38 and a thickness ofapproximately 0.15λ₁, and a second dielectric layer (not shown) formedof TiO₂ having a refractivity of approximately 2.3 and a thickness ofapproximately 0.25λ₁, where λ₁ indicates a reference wavelength ofapproximately 660 nm. As a result, the first or second slant reflectionsurface 51 or 53 reflects most of the light that has a wavelength of 410mn.

Therefore, if the position of the first light source 25 is changed withthat of the second light source 35, the second slant reflection surface53 reflects most of the light beam having a wavelength of 780 nm that isemitted from the third light source 45, and transmits most of the lightbeams having wavelengths of 410 nm and 650 nm that are emitted from thefirst and the second light sources 25 and 35, respectively.

Likewise, if the position of the first light source 25 is changed withthat of the third light source 45, the first slant reflection surface 51reflects most of the light beam having a wavelength of 650 nm that isemitted from the second light source 35, and transmits most of the lightbeams having wavelengths of 410 nm and 780 nm that are emitted from thefirst and the third light sources 25 and 45.

As illustrated in FIG. 1, the converging device 60 includes a firstobject lens 61 and a second object lens 63 corresponding to recordingmedia 10 of different thicknesses, and an actuator 65 that selectivelylocates the first and the second object lenses 61 and 63 with respect tothe corresponding recording media 10. The actuator 65 controls focusingand tracking positions of the first object lens 61 and the second objectlens 63 with respect to the recording media 10.

The first object lens 61 is appropriate for recording and/or reproducingusing a relatively thin recording medium 10 a, such as a HD-DVD, and thesecond object lens 63 is appropriate for recording and/or reproducingusing a relatively thick recording medium 10 b, such as a CD. If thethickness of the HD-DVD is the same as the thickness of the DVD, thefirst object lens 61 may be used for recording and reproducing the DVD.When the DVD is recorded and/or reproduced by the first object lens 61for a HD-DVD, the distance between the first object lens 61 and thesecond hologram element 39 is optimized so that chromatic aberrationcaused by a wavelength difference is corrected. If the thickness of theHD-DVD is different from the thickness of the DVD, an object lens (notshown) appropriate for being optimized with respect to the wavelength ofthe light beam emitted from the second light source 35 to record and/orreproduce the DVD may be further provided.

In the compatible optical pick-up apparatus of the present invention,the first light source 25 or the second light source 35 is operatedduring recording and/or reproducing of the HD-DVD or the DVD, and thefirst object lens 61 is arranged along a light path between therecording medium 10 a and the dichroic beam splitter 50 by the actuator65. The light beam that is emitted from the first light source 25 istrasmitted through the dichroic beam splitter 50, and the transmittedlight beam is converged by the first object lens 61 to form a light spoton a recording surface of the recording medium 10 a. Subsequently, thelight beam reflected from the recording medium 10 a passes through thedichroic beam splitter 50 to be input to the first photodetector 27. Inaddition, the light beam emitted from the second light source 35 isreflected from the first slant reflection surface 51 to form a lightspot on a recording surface of the recording medium 10 a. The light beamreflected from the recording medium 10 a is then reflected from thefirst slant reflection surface 51 to be input to the secondphotodetector 37.

The third light source 45 is operated during recording/reproducing of aCD, with the second object lens 63 being positioned along a light pathbetween the recording medium 10 and the dichroic beam splitter 50 by theactuator 65. The light beam emitted from the third light source 45 isreflected from the second slant reflection surface 53 of the dichroicbeam splitter 50, and the reflected light is converged by the secondobject lens 63 to form a light spot on a recording surface of recordingmedia 10 b. Subsequently, the light beam reflected from the recordingmedium 10 b is reflected from the second slant surface 53 to be input tothe third photodetector 47.

In the above-described compatible optical pick-up apparatus, the HD-DVD,DVD family, including the DVD-R, and the CD family, including the CD-Rcan be compatibly employed.

FIG. 3 is a schematic view of another type of converging device 60 awhich may be used in the optical pick-up apparatus shown in FIG. 1. Asillustrated in FIG. 3, an object lens 67 in which an annular lightcontrol pattern 67 a is formed may be employed as the converging device60 a. The light control pattern 67 a may be variously modified asneeded.

During operation of the optical pick-up apparatus of FIG. 3, a lightbeam passing through an inside portion of the light control pattern 67 aforms a light spot on a recording surface of the relatively thickrecording medium 10 b, which may be a CD, and a light beam passingthrough an outside portion of the light control pattern 67 a forms alight spot on a recording surface of a relatively thin recording media10 a, which includes an HD-DVD and/or a DVD.

If the thickness of the HD-DVD is different from the thickness of theDVD, a light control pattern (not shown) corresponding to the DVD may befurther formed on the object lens 67.

FIG. 4 is a schematic view of the optical arrangement of a compatibleoptical pick-up apparatus according to a second embodiment of thepresent invention. Reference numerals of FIG. 4 that are the same asthose of FIG. 1 indicate the same elements of FIG. 1, and therefore adescription of those parts is omitted.

As illustrated in FIG. 4, the optical pick-up apparatus according to thesecond embodiment of the present invention employs a dichroic beamsplitter 150 that includes a single slant reflection surface 153 thattransmits and reflects a light beam emitted from the first light source25 for a HD-DVD, and the third light source 45 for a CD. The dichroicbeam splitter 150 is formed by bringing two prisms into contact witheach other, and the slant reflection surface 153 is formed in the samemanner as the first slant surface 53 of FIG. 1. The slant reflectionsurface 153 transmits most of the light beam that has a wavelength ofapproximately 410 nm that is emitted from the first light source 25, andreflects most of the light beam that has a wavelength of approximately780 nm that is emitted from the third light source 45.

If a position of the first light source 25 is changed with a position ofthe third light source 45, the slant reflection surface 153 reflectsmost of the light beam that has a wavelength of 410 nm that is emittedfrom the first light source 25, and transmits most of the light beamthat has a wavelength of 780 nm emitted from the third light source 45.The object lens 67 described with reference to FIG. 3 may be employed asthe converging device 60.

During operation of the compatible optical pick-up apparatus of FIG. 4,the first light source 25 is operated during recording and/orreproduction of an HD-DVD, and the third light source 45 is operatedduring recording and/or reproduction of a CD. The optical pick-upapparatus can record and reproduce HD-DVD and CD related devicesincluding a CD-R. In addition, DVD related devices, except a DVD-R, canalso be recorded and reproduced by the first light source 25.

FIG. 5 is a schematic view of an optical arrangement of a compatibleoptical pick-up apparatus according to a third embodiment of the presentinvention. Reference numerals of FIG. 5 that are the same as those ofFIG. 4 indicate the same elements as those of FIG. 4, and therefore adescription of those parts has been omitted. In the optical pick-upapparatus of FIG. 5, an HD-DVD and a DVD can be compatibly employed.That is, the optical pick-up apparatus of FIG. 5 includes the firstlight source 25 to emit light beams for an HD-DVD, the second lightsource 35 to emit light beams for a DVD, and a dichroic beam splitter250 that includes a slant reflection surface 251 for transmitting andreflecting light beams emitted from the first and second light sources25 and 35.

An object lens 161 appropriate for recording and/or reproducing anHD-DVD, and an actuator 165 for controlling focusing and trackingpositions of the object lens 161, are employed as a converging device160.

The dichroic beam splitter 250 is formed by bringing two prisms intocontact with each other, and the slant reflection surface 251 is formedin the same manner as the first slant reflection surface 51 of FIG. 1.The slant reflection surface 251 transmits most of the light beam thathas a wavelength of approximately 410 nm that is emitted from the firstlight source 25, and reflects most of the light beam that has awavelength of approximately 650 nm that is emitted from the second lightsource 35.

If a position of the first light source 25 is changed with a position ofthe second light source 35, the slant reflection surface 251 reflectsmost of the light beam that has a wavelength of 410 nm that are emittedfrom the first light source 25, and transmits most of the light beamthat has a wavelength of 650 nm that is emitted from the second lightsource 35.

During operation of the optical pick-up apparatus according to FIG. 5,the first light source 25 is operated during recording and reproductionof an HD-DVD, and the second light source 35 is operated duringrecording and reproduction of a DVD. The compatible optical pick-upapparatus can record and/or reproduce a DVD related device, including aDVD-R and an HD-DVD.

If the thickness of the HD-DVD is different from the thickness of theDVD, the converging device 160 also includes an object lens (not shown)that is appropriate for recording and reproducing a DVD, or an objectlens (not shown) in which a light control pattern that is appropriatefor an HD-DVD and a DVD is formed, may be employed.

According to the compatible optical pick-up apparatus of the presentinvention, a plurality of light sources radiating light beams havingvarious wavelengths and a dichroic beam splitter for selectivelytransmitting and reflecting light beams having various wavelengths areprovided, to thereby record information on and reproduce from recordingmedia that have various formats.

What is claimed is:
 1. An optical pick-up apparatus for recording and/orreproducing information from first through third recording media,comprising: a first light source to emit a light beam having awavelength corresponding to the first recording medium when the firstrecording medium is accessed; a second light source to emit a light beamhaving a wavelength corresponding to the second recording medium whenthe second recording medium is accessed; a third light source to emit alight beam having a wavelength corresponding to the third recordingmedium when the third recording medium is accessed; a dichroic beamsplitter having first through third input surfaces to receive the lightemitted from the first through third light sources, respectively,dielectric surfaces to receive the light from the first through thirdinput surfaces, and an output surface through which the light beamsreceived by the first through third input surfaces and the dielectricsurfaces are transmitted toward the first, the second, and the thirdrecording media, respectively, each dielectric surface comprisingrepeated stacks of dielectric layers; a converging device to convergeeach of the light beams transmitted through the output surface of thedichroic beam splitter toward the respective first through thirdrecording media; and first through third photodetectors to respectivelyreceive the light beams reflected from the respective first throughthird recording media and which pass through the dichroic beam splitter.2. The optical pick-up apparatus of claim 1, wherein the light beamsemitted by the first through third light sources have wavelengths ofapproximately 410 nm, 650 nm and 780 nm, respectively.
 3. The opticalpick-up apparatus of claim 1, wherein the dichroic beam splittercomprises: a first slant reflection surface to transmit the light beamemitted from the first light source, and to reflect the light beamemitted from the second light source, toward the output surface; and asecond slant reflection surface to transmit the light beam emitted fromthe first light source, and to reflect the light beam emitted from thethird light source, toward the output surface.
 4. The optical pick-upapparatus of claim 1, wherein the converging device comprises: aplurality of object lenses to converge the light beams emitted from thecorresponding first, second and third light sources transmitted throughthe dichroic beam splitter to the first, the second, and the thirdrecording media, respectively; and an actuator to selectively locate theplurality of object lenses in accordance with a thickness of the first,the second, or the third recording media to be accessed along a lightpath.
 5. The optical pick-up apparatus of claim 1, wherein theconverging device includes an object lens having an annular lightcontrol pattern.
 6. The optical pick-up apparatus of claim 1, whereinsaid first through third light sources define first through thirdemitted light optical paths to the respective first through thirdrecording media; and said first through third photodetectors definefirst through third reflected light optical paths from the respectivefirst through third recording media, the first through third reflectedlight optical paths being substantially parallel to the first throughthird emitted light optical paths through said dichroic beam splitter.7. An optical pick-up apparatus for recording and/or reproducinginformation from first through third recording media, comprising: afirst light source to emit a light beam having a wavelengthcorresponding to the first recording medium when the first recordingmedium is accessed; a second light source to emit a light beam having awavelength corresponding to the second recording medium when the secondrecording medium is accessed; a third light source to emit a light beamhaving a wavelength corresponding to the third recording medium when thethird recording medium is accessed; a dichroic beam splitter havingfirst through third input surfaces to receive the light emitted from thefirst through third light sources, respectively, and an output surfacethrough which the light beams received by the first through third inputsurfaces are transmitted toward the first, the second, and the thirdrecording media, respectively; a converging device to converge each ofthe light beams transmitted through the output surface of the dichroicbeam splitter toward the respective first through third recording media;and first through third photodetectors to respectively receive the lightbeams reflected from the respective first through third recording mediaand which pass through the dichroic beam splitter, wherein: the dichroicbeam splitter comprises: a first slant reflection surface to transmitthe light beam emitted from the first light source, and to reflect thelight beam emitted from the second light source, toward the outputsurface; and a second slant reflection surface to transmit the lightbeam emitted from the first light source, and to reflect the light beamemitted from the third light source, toward the output surface, and eachof the first and the second slant reflection surfaces comprisesrepeatedly stacked dielectric layers, each having a refractivitydifferent from an adjacent one of the dielectric layers.
 8. The opticalpick-up apparatus of claim 7, wherein the dielectric layers alternatelycomprise MgF₂ and TiO₂, SiO₂ and ZrO₂, Al₂O₃ and ZrO₂, MgF₂ and ZrO₂,SiO₂ and TiO₂, or Al₂O₃ and TiO₂.
 9. The optical pick-up apparatus ofclaim 7, wherein one of the first and the second slant reflectionsurfaces comprises repeatedly alternated stacks of a first dielectriclayer having a refractivity of approximately 1.38 and a thickness of0.3λ₁ and a second dielectric layer having a refractivity ofapproximately 2.3 and a thickness of 0.5λ₁, wherein λ₁ indicates a firstreference wavelength of approximately 1040 nm, and the other one of thefirst and the second slant reflection surfaces comprises repeatedlyalternated stacks of a third dielectric layer having a refractivity ofapproximately 1.38 and a thickness of 0.3λ₂ and a fourth dielectriclayer having a refractivity of approximately 2.3 and a thickness of0.5λ₂, wherein λ₂ indicates a second reference wavelength ofapproximately 600 nm.
 10. The optical pick-up apparatus of claim 7,wherein one of the first and the second slant reflection surfacescomprises repeatedly alternated stacks of a first dielectric layerhaving a refractivity of approximately 1.38 and a thickness of 0.15λ₁and a second dielectric layer having a refractivity of approximately 2.3and a thickness of 0.25λ₁, wherein λ₁ indicates a first referencewavelength of approximately 660 nm, and the other one of the first andthe second slant reflection surfaces comprises repeatedly alternatedstacks of a third dielectric layer having a refractivity ofapproximately 1.38 and a thickness of 0.3λ₂ and a fourth dielectriclayer having a refractivity of approximately 2.3 and a thickness of0.5λ₂, wherein λ₂ indicates a second reference wavelength ofapproximately 600 nm.
 11. The optical pick-up apparatus of claim 7,wherein one of the first and the second slant reflection surfacescomprises repeatedly alternated stacks of a first dielectric layerhaving a refractivity of approximately 1.38 and a thickness of 0.15λ₁and a second dielectric layer having a refractivity of approximately 2.3and a thickness of 0.25λ₁, wherein λ₁ indicates a first referencewavelength of approximately 660 nm, and the other one of the first andthe second slant reflection surfaces comprises repeatedly alternatedstacks of a third dielectric layer having a refractivity ofapproximately 1.38 and a thickness of 0.3λ₂ and a fourth dielectriclayer having a refractivity of approximately 2.3 and a thickness of0.5λ₂, wherein λ₂ indicates a second reference wavelength ofapproximately 1040 nm.
 12. An optical pick-up apparatus for recordingand/or reproducing information from first and second recording media,comprising: a first light source to emit a light beam having a firstwavelength when the first recording medium is accessed, and a secondlight source to emit a light beam having a second wavelength when thesecond recording medium is accessed, the first and the secondwavelengths corresponding to the first and second recording media; adichroic beam splitter having first and second input surfaces to receivethe light beams emitted from the first and second light sources,respectively, and an output surface through which the light beamsreceived by the first and second input surfaces are transmitted towardthe first and second recording media, respectively; a converging deviceto converge each of the light beams transmitted through the outputsurface of the dichroic beam splitter to the respective first and thesecond recording media; and first and second photodetectors torespectively receive the light beams reflected from the respective firstand second recording media and which pass through the dichroic beamsplitter, wherein: the dichroic beam splitter includes a slantreflection surface consisting of repeatedly alternated stacks of firstand second dielectric layers, each of the first and second dielectriclayers having corresponding first and second thicknesses such that theslant reflection surface transmits and reflects the light beams emittedfrom the first and second light source to the output surface, the firstand second light sources emit light beams having wavelengths ofapproximately 419 nm and 650 nm, respectively, and the first dielectriclayer has a refractivity of 1.38 and a thickness of 0.3λ₁, and thesecond dielectric layer has a refractivity of 2.3 and a thickness of0.5λ₁, wherein λ₁ indicates a reference wavelength of approximately 1040nm.
 13. An optical pick-up apparatus for recording and/or reproducinginformation from first and second recording media, comprising: a firstlight source to emit a light beam having a first wavelength when thefirst recording medium is accessed, and a second light source to emit alight beam having a second wavelength when the second recording mediumis accessed, the first and the second wavelengths corresponding to thefirst and second recording media; a dichroic beam splitter having firstand second input surfaces to receive the light beams emitted from thefirst and second light sources, respectively, and an output surfacethrough which the light beams received by the first and second inputsurfaces are transmitted toward the first and second recording media,respectively; a converging device to converge each of the light beamstransmitted through the output surface of the dichroic beam splitter tothe respective first and the second recording media; and first andsecond photodetectors to respectively receive the light beams reflectedfrom the respective first and second recording media and which passthrough the dichroic beam splitter, wherein: the dichroic beam splitterincludes a slant reflection surface consisting of repeatedly alternatedstacks of first and second dielectric layers, each of the first andsecond dielectric layers having corresponding first and secondthicknesses such that the slant reflection surface transmits andreflects the light beams emitted from the first and second light sourceto the output surface, the first and second light sources emit lightbeams having wavelengths of approximately 410 nm and 650 nm,respectively, and the first dielectric layer has a refractivity of 1.38and a thickness of 0.15λ₁, and the second dielectric layer has arefractivity of 2.3 and a thickness of 0.25λ₁, wherein λ₁ indicates areference wavelength of approximately 660 nm.
 14. An optical pick-upapparatus for recording and/or reproducing information from first andsecond recording media, comprising: a first light source to emit a lightbeam having a first wavelength when the first recording medium isaccessed, and a second light source to emit a light beam having a secondwavelength when the second recording medium is accessed, the first andthe second wavelengths corresponding to the first and second recordingmedia; a dichroic beam splitter having first and second input surfacesto receive the light beams emitted from the first and second lightsources, respectively, and an output surface through which the lightbeams received by the first and second input surfaces are transmittedtoward the first and second recording media, respectively; a convergingdevice to converge each of the light beams transmitted through theoutput surface of the dichroic beam splitter to the respective first andthe second recording media; and first and second photodetectors torespectively receive the light beams reflected from the respective firstand second recording media and which pass through the dichroic beamsplitter, wherein: the dichroic beam splitter includes a slantreflection surface consisting of repeatedly alternated stacks of firstand second dielectric layers, each of the first and second dielectriclayers having corresponding first and second thicknesses such that theslant reflection surface transmits and reflects the light beams emittedfrom the first and second light source to the output surface, the lightbeams emitted from the first and the second light sources havewavelengths of approximately 410 nm and 780 nm, respectively, and thefirst dielectric layer has a refractivity of approximately 1.38 and athickness of 0.15λ₁, and the second dielectric layer has a refractivityof approximately 2.3 and a thickness of 0.25λ₁, wherein λ₁ indicates areference wavelength of approximately 660 nm.
 15. An optical pick-upapparatus for recording and/or reproducing information from first andsecond recording media, comprising: a first light source to emit a lightbeam having a first wavelength when the first recording medium isaccessed, and a second light source to emit a light beam having a secondwavelength when the second recording medium is accessed, the first andthe second wavelengths corresponding to the first and second recordingmedia; a dichroic beam splitter having first and second input surfacesto receive the light beams emitted from the first and second lightsources, respectively, and an output surface through which the lightbeams received by the first and second input surfaces are transmittedtoward the first and second recording media, respectively; a convergingdevice to converge each of the light beams transmitted through theoutput surface of the dichroic beam splitter to the respective first andthe second recording media; and first and second photodetectors torespectively receive the light beams reflected from the respective firstand second recording media and which pass through the dichroic beamsplitter, wherein: the dichroic beam splitter includes a slantreflection surface consisting of repeatedly alternated stacks of firstand second dielectric layers, each of the first and second dielectriclayers having corresponding first and second thicknesses such that theslant reflection surface transmits and reflects the light beams emittedfrom the first and second light source to the output surface, the lightbeams emitted from the first and the second light sources havewavelengths of approximately 410 nm and 780 nm, respectively, and thefirst dielectric layer has a refractivity of approximately 1.38 and athickness of 0.3λ₁, and the second dielectric layer has a refractivityof approximately 2.3 and a thickness of 0.5λ₁, wherein λ₁ indicates areference wavelength of approximately 600 nm.
 16. An optical pick-updevice to record and/or reproduce information from a plurality ofrecording media of different formats, one of which is to be accessed ata given time, the optical pick-up device comprising: first, second, andthird light sources to emit light beams of different wavelengthscorresponding respectively to the plurality of recording media,depending upon which one of the plurality of recording media is to beaccessed; a dichroic beam splitter including first and second slantreflection surfaces oblique to the light beams of the first, second, andthird light sources and which selectively reflect and transmit the lightbeams of first, second, and third light sources based upon thewavelengths of the light beams of the first, second, and third lightsources; a converging device to converge each of the light beamstransmitted from the dichroic beam splitter to the recording media; anda plurality of photodetectors to respectively receive the light beamsreflected from the plurality of recording media and which pass throughthe converging device and the dichroic beam splitter and are incidentupon the at least one slant reflection surface, wherein: the first slantreflection surface comprises repeatedly alternated stacks of first andsecond dielectric layers, wherein the first and second dielectric layershave different refractivities, the first slant reflection surfacetransmits the light beam emitted from the first light source, andreflects the light beam emitted from the second light source, toward theoutput surface, and the second slant reflection surface comprisesrepeatedly alternated stacks of third and fourth dielectric layers,wherein the third and fourth dielectric layers have differentrefractivities, the second slant reflection surface transmits the lightbeam emitted from the first light source, and reflects the light beamemitted from the third light source, toward the output surface.
 17. Anoptical pick-up device to record and/or reproduce information from aplurality of recording media of different formats, one of which is to beaccessed at a given time, the optical pick-up device comprising: firstand second light sources to emit light beams of different wavelengthscorresponding respectively to the plurality of recording media,depending upon which one of the plurality of recording media is to beaccessed; a dichroic beam splitter including a slant reflection surfaceoblique to the light beams of the first and second light sources andwhich selectively reflects and transmits the light beams of the firstand second light sources based upon the wavelengths of the light beamsof the first and second light sources; a converging device to convergeeach of the light beams transmitted from the dichroic beam splitter tothe recording media; and a plurality of photodetectors to respectivelyreceive the light beams reflected from the plurality of recording mediaand which pass through the converging device and the dichroic beamsplitter and are incident upon the at least one slant reflectionsurface, wherein the slant reflection surface consists of repeatedlyalternated stacks of first and second dielectric layers, wherein thefirst and second dielectric layers have corresponding first and secondthicknesses, the slant reflection surface transmits the light beamemitted from the first light source, and reflects the light beam emittedfrom the second light source.